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                    AJ Utils
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                <h1>JsonUtil Tutorial</h1>
<p>This tutorial provides an overview of the <code>JsonUtil</code> class, which is part of the <code>lightweight-component/aj-util</code> library. The <code>JsonUtil</code> class provides utility methods for working with JSON data in Java applications.</p>
<h2>Introduction</h2>
<p>The <code>JsonUtil</code> class contains static methods for common JSON operations using Jackson library, including conversion between JSON strings, Java objects, Maps, and Lists.</p>
<h2>Main Features</h2>
<ul>
<li>Convert Java objects to JSON strings (pretty or compact)</li>
<li>Parse JSON strings into Java objects</li>
<li>Convert between JSON and Maps/Lists</li>
<li>Type-safe JSON processing</li>
<li>Java 8 date/time support</li>
<li>Strict duplicate detection</li>
</ul>
<h2>Methods</h2>
<h3>1. Serialization (to JSON)</h3>
<ol>
<li><code>toJson(Object obj)</code> - Convert object to JSON string</li>
<li><code>toJsonPretty(Object obj)</code> - Convert object to pretty-printed JSON</li>
</ol>
<h3>2. Deserialization (from JSON)</h3>
<ol>
<li><code>fromJson(String jsonStr, Class&lt;T&gt; valueType)</code> - Parse JSON to specified type</li>
<li><code>fromJson(String jsonStr, JavaType valueType)</code> - Parse JSON with complex type</li>
</ol>
<h3>3. JSON ↔ Map Conversion</h3>
<ol>
<li><code>json2map(String jsonStr)</code> - JSON to Map&lt;String, Object&gt;</li>
<li><code>json2map(String jsonStr, Class&lt;T&gt; clazz)</code> - JSON to Map with typed values</li>
<li><code>json2sortMap(String jsonStr, Class&lt;T&gt; clazz)</code> - JSON to LinkedHashMap preserving order</li>
<li><code>json2StrMap(String jsonStr)</code> - JSON to Map&lt;String, String&gt;</li>
</ol>
<h3>4. JSON ↔ List Conversion</h3>
<ol>
<li><code>json2list(String jsonArrayStr, Class&lt;T&gt; clazz)</code> - JSON array to List<T></li>
<li><code>json2mapList(String jsonArrayStr)</code> - JSON array to List<Map></li>
</ol>
<h3>5. Object Conversion</h3>
<ol>
<li><code>convertValue(Object obj, Class&lt;T&gt; clazz)</code> - Convert object types</li>
<li><code>pojo2map(Object obj)</code> - Convert POJO to Map</li>
<li><code>pojo2map(Object obj, Class&lt;T&gt; clazz)</code> - Convert POJO to typed Map</li>
<li><code>map2pojo(Map&lt;String, Object&gt; map, Class&lt;T&gt; clazz)</code> - Convert Map to POJO</li>
</ol>
<h3>6. JSON Tree Model</h3>
<ol>
<li><code>json2Node(String jsonStr)</code> - Parse JSON to JsonNode tree</li>
</ol>
<h2>Usage Examples</h2>
<h3>Basic Serialization</h3>
<pre><code class="language-java">User user = new User(&quot;John&quot;, 30);
String json = JsonUtil.toJson(user); 
// {&quot;name&quot;:&quot;John&quot;,&quot;age&quot;:30}

String prettyJson = JsonUtil.toJsonPretty(user);
/*
{
  &quot;name&quot; : &quot;John&quot;,
  &quot;age&quot; : 30
}
*/
</code></pre>
<h3>Basic Deserialization</h3>
<pre><code class="language-java">String json = &quot;{\&quot;name\&quot;:\&quot;John\&quot;,\&quot;age\&quot;:30}&quot;;
User user = JsonUtil.fromJson(json, User.class);
</code></pre>
<h3>Map Conversion</h3>
<pre><code class="language-java">Map&lt;String, Object&gt; map = new HashMap&lt;&gt;();
map.put(&quot;name&quot;, &quot;John&quot;);
map.put(&quot;age&quot;, 30);

String json = JsonUtil.toJson(map);
Map&lt;String, Object&gt; map2 = JsonUtil.json2map(json);
</code></pre>
<h3>List Conversion</h3>
<pre><code class="language-java">String jsonArray = &quot;[{\&quot;name\&quot;:\&quot;John\&quot;}, {\&quot;name\&quot;:\&quot;Alice\&quot;}]&quot;;
List&lt;User&gt; users = JsonUtil.json2list(jsonArray, User.class);
</code></pre>
<h2>Configuration</h2>
<p>The <code>JsonUtil</code> class is pre-configured with:</p>
<ul>
<li>Java 8 date/time support</li>
<li>Strict duplicate detection</li>
<li>Asia/Shanghai timezone</li>
<li>Default ObjectMapper instance</li>
</ul>
<h2>Conclusion</h2>
<p>The <code>JsonUtil</code> class provides comprehensive utility methods for working with JSON data, making it easier to serialize, deserialize, and convert between JSON and Java objects.</p>

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